The field of the invention is float activated gauges. The invention appears to be especially well suited to providing float activated gauges for indicating the quantity of fuel in a fuel tank.
A common type of prior float activated gauge is depicted in U. S. Pat. 1,371,395. It comprises a float with indexing grooves which ride in a pair of guide rods, one guide rod on each side of the float. The float is thereby free to move vertically, but is restrained from twisting or rolling. A helically shaped twisted strip is disposed between the guide rods and passes through a precision slot in the float, the slot closely conforming to the cross section of the twisted strip.
As the float moves vertically, due to a change in the height of fuel in the tank, the twisted strip is forced to rotate since the float is restrained from rotating. A pointer is attached onto the end of the twisted strip and is disposed in a transparent cap. The position of the pointer is then calibrated with marking indicia to indicate the quantity of fuel in the tank.
The manufacture of such gauges is somewhat complicated in the following respects. First, the twisted strip must be thin, so that it will accurately follow in the mating slot on the float. Because the strip passes through the flot, the strip must additionally be narrow so that the float can be as small as possible. Given the forces placed on the strip, it must also be quite rigid. Thus, it is typically made of metal. Less expensive materials, for example, plastics, are not as suitable.
Secondly, the float must be formed in a precision manner, including the guide slots, the slot mating to the twisted strap, and a counterbore, or well, so that the slot portion only engages a small vertical section of the twisted strap, Operational problems may also be caused by the narrow hole in the float, for example, by jamming due to debris or due to rust or deformation of the strip.